Duke of Lower Lorraine

The rulers of Lorraine have held different posts under different governments over different regions. The first rulers of the region were kings of the Franks whose kingdom was called Lotharingia. The Latin construction "Lotharingia" evolved over time into "Lorraine" in French, "Lotharingen" in Dutch and "Lothringen" in German. After the Carolingian kingdom was absorbed into its neighbouring realms in the late ninth century, dukes were appointed over the territory. In the mid-tenth century, the duchy was divided into Lower Lorraine and Upper Lorraine, the first evolving into the historical Low Countries, the second became known as the Duchy of Lorraine and existed well into the modern era.

Charles the Bald claimed Lotharingia on Lothair's death and was crowned king in Metz, but his brother Louis the German opposed his claim and in 870 the Treaty of Mersen divided Lotharingia between the two brothers and subsequently their sons. In 880, the Treaty of Ribemont gave the whole of Lotharingia to Louis the Younger, son of Louis the German.

In 925, Lotharingia was subsumed into East Francia.

In 959, Lorraine was divided into two districts: Upper and Lower, each being given to a margrave or vice-duke under Bruno. Upon Bruno's death in 965, that of Lower Lorraine, whose margrave had died, was left vacant until 977. In that year Charles was appointed duke of Lower Lorraine and Frederick I was elevated duke in Upper Lorraine. The two duchies remained separate, following separate pathways, except for the brief period between 1033 and 1044.

Junior branch of the previous rulers of Ardennes–Metz, known as the House of Lorraine

The House of Habsburg-Lorraine continued carrying the title as titular Dukes of Lorraine.

...
Wikipedia